There are a variety of contexts where electrical components are included in an optical system. Conventionally, the electrical components are placed on the edge of the optical system so that the electrical components don't block or otherwise interfere with the light propagating through the optical system. In the case of an augmented reality (AR) or mixed reality (MR) headset, a user may be viewing computer generated images as well as viewing scene light from the ambient environment. In this particular case, illuminating the eye of the user for eye-tracking purposes enhances the viewing experience. However, conventional designs place the illumination light sources on the edges of the field of view of the user so that the illumination light sources (and corresponding routing) don't introduce noticeable occlusions into the field of view of the user, even when it may be advantageous to place the illumination light sources in the field of view.